Born on Jan. 11, 1887, Aldo Leopold, an influential American scientist and conservationist and the author of "A Sand County Almanac" (more than 2 million copies of which have been sold since it was released in 1949), continues to influence writers and thinkers in modern times.

Leopold is regarded as the founder of the science of wildlife management. "The Land Ethic," a chapter of his book, popularized the idea of ecological thinking — that animals, plants, soil, geology, water and climate all come together to form a community of life — that they are not separate parts, but integrated pieces of a whole.

His understanding of the natural world is captured in many of his quotes, a collection of which are gathered below — a fitting tribute on what would have been his 129th birthday.

"Harmony with land is like harmony with a friend; you cannot cherish his right hand and chop off his left." - Aldo Leopold

In the summers, Aldo Leopold's parents took the family to the Les Cheneaux Islands area of Michigan's Upper Peninsula, where the children had free range to explore the natural world. (Photo: Scott Smithson/flickr)

Leopold's early life included lots of time outdoors with his father and siblings in Iowa (and summers in the Les Cheneaux Islands of Michigan's Upper Peninsula); he was a strong student and spent hours outside counting and cataloguing birds.

"We abuse land because we see it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect.”

By the age of 24, Leopold had been promoted to the role of supervisor for the Carson National Forest in New Mexico, pictured above. (Photo: Greg Westfall/flickr)

Leopold went on to study at the then-new Yale School of Forestry, and from there he went into a career with the Forest Service, where he spent more than a decade in New Mexico and Arizona. He went on to develop the first comprehensive management plan for the Grand Canyon.

“We reached the old wolf in time to watch a fierce green fire dying in her eyes. I realized then, and have known ever since, that there was something new to me in those eyes – something known only to her and to the mountain. I was young then, and full of trigger-itch; I thought that because fewer wolves meant more deer, that no wolves would mean hunters’ paradise. But after seeing the green fire die, I sensed that neither the wolf nor the mountain agreed with such a view.”

Wolves affect myriad systems around them, from direct prey populations to other flora and fauna with which they share their ecosystems, recent research has shown. (Photo: Wiki Commons)

Leopold recognized the importance of apex predators like bears and wolves decades before this idea was more commonly accepted (though in some places, that's still an ongoing battle). He wrote about this concept of trophic cascade in a chapter of "The Sand County Almanac" called "Thinking Like a Mountain" when he realizes the implications of killing a wolf.

“One of the penalties of an ecological education is that one lives alone in a world of wounds. Much of the damage inflicted on land is quite invisible to laymen. An ecologist must either harden his shell and make believe that the consequences of science are none of his business, or he must be the doctor who sees the marks of death in a community that believes itself well and does not want to be told otherwise.”

When you see Grand Teton, you don't question the importance of saving wild places, and Leopold championed the idea. (Photo: Dave Hensley/flickr)

Leopold also saw the future wrought by a world filled with automobiles (and roads) crisscrossing the country, and the demands of a rapidly increasing population. He wanted to protect large areas for their own sake, away from human development (including roads) and was the first person to use the world "wilderness" to describe the idea.

“The last word in ignorance is the man who says of an animal or plant: 'What good is it?”

Are animals, like this elk, valuable only inasmuch as they can be bought or sold by human beings, or do they have inherent value? Leopold advocated the latter idea. (Photo: Josef Pittner/Shutterstock)

Leopold rejected the utilitarian viewpoint that many conservationists of his time held, who used the ideas of how valuable a piece of land was — in mineral rights, animals that could be hunted, or how rich a river was with fish — to judge its worth. He believed animals, plants and natural systems had worth in the own right.

"A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise."

Aldo Leopold Shack near the Wisconsin Dells in Wisconsin on land that he and his family restored over time from a barren landscape. (Photo: Jonathunder/Wikimedia Commons)

Leopold moved to Wisconsin in 1933, and he and his family began an experiment of their own — on 80 acres of land that had been logged, consumed by several wildfires, over-grazed by cattle and finally left barren, they planted thousands of pine trees, and worked on restoring prairie areas. Following the rehabilitation of landscape along the Wisconsin River gave Leopold a greater understanding of how natural systems worked and inspired him to write "A Sand County Almanac" later.

“Our ability to perceive quality in nature begins, as in art, with the pretty. It expands through successive stages of the beautiful to values as yet uncaptured by language.”

Half the Gila National Forest, first protected in 1924, was named after Leopold after he passed away. (Photo: Zack Frank/Shutterstock)

Though Leopold died in 1948 at the age of 61, a wilderness area was named after him in 1980. The Aldo Leopold Wilderness comprises more than 200,000 acres in the Gila National Forest of New Mexico.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.

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